New smartphone breakthrough promises to double battery life

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Wireless communication has changed the world in recent decades, but there has been a very basic problem slowing progress this whole time. All wireless devices — from the massive transmission towers you drive by on the road, to the phone in your pocket — have a catastrophically inefficient power amplifier inside that’s used to turn electricity into radio waves. A start-up associated with MIT claims to have solved the problem, and is almost ready to deploy the technology.

Eta Devices, a Massachusetts-based company founded by two MIT professors, says its new technology can double the efficiency of wireless power amplifiers. These components are currently sitting at about 30-35% efficiency in modern telecom equipment. As much as 60% of a smartphone’s battery usage can go to the power amplifier, so you can see how this could be a huge leap forward.

If you’ve ever used a smartphone to send a large amount of data, the device probably got a little warm in your hand. As your wireless radio shoots bits into the air, all that heat is essentially the wasted energy due to inefficient power amplifiers. The next time your phone runs out of juice halfway through the day, you can probably blame the amplifier.

So why does this happen? Power amplifiers use transistors that operate in two basic modes: standby and output. If you’re not actively using your cellular radio, the amplifier stays in standby and uses less power. Output mode will obviously use more power, but the standby mode used in current technologies is abnormally high. The reason: jumping from low to high-power causes signal distortion, but this effect is lessened by using a higher power standby mode. That’s why current power amplifiers waste so much energy.

The innovation being worked out by Eta Devices is basically a super-fast voltage regulator. This device will choose the most efficient energy level required for the power amplifier’s activities and sends it across the transistor. It can do this 20 million times per second, resulting in a much more efficient use of available energy. Eta calls this technology “asymmetric multilevel outphasing.”

It’s not just the transmission of data that could be made more efficient by this technology, but receiving data too. Even when you’re not sending a lot of packets, your device is transmitting confirmations of packet arrival to the remote server (this is TCP traffic management). That means your power amplifier is still cranked up in high-power mode even though you’re not sending data. Knowing this, Eta hopes to design a single amplifier chip that could handle all the wireless standards currently in use. That would be a boon for smartphones, which often have amplifiers built in for each of several radios.

Asymmetric multilevel outphasing is currently on track to get trial runs in 2013, but not in phones. Eta Devices is first targeting cellular bay stations, likely those based on LTE. Fully two-thirds of total power consumed by these units goes to the power amplifier — and they use a lot of power. The opportunity for energy savings is much greater at the infrastructure level, but large scale implementation of this technology will teach Eta how to make it work in pocket-sized packages.